Is it permissible for a male cousin to prevent his female cousin's brother and her brother's children from visiting her, while she is residing with him?

Maintaining ties with the aunt and sister is obligatory. One must strive to visit them and communicate with them, and address the actions of her son in the best possible manner, explaining to him the Islamic ruling. If he insists on preventing entry to his home, then it is not permissible to enter without his permission. The mother can be called outside the house to greet her or to host her, because the mother is not obliged to obey her son in severing kinship ties.